1. Field of the Invention
The present invention relates to a bearing with a noncontact signal transfer mechanism. More particularly, the present invention relates to a bearing with a noncontact signal transfer mechanism transmitting a measurement signal, for example, when the physical property such as the temperature of a rotor is measured, to a stationary side in a noncontact manner.
2. Description of the Background Art
In the measuring process of physical property such as the temperature of a shaft supported by a bearing or the like or of a rotor attached to such a shaft, it is necessary to feed power to a sensor and associated electronic circuitry used for the measurement as well as to provide the obtained sensor signal output, a control signal or the like. To this end, slip rings and brushes are employed.
In the case where power is fed and signals are transmitted/received via a contact type brush and slip ring, these components must be exchanged periodically due to the friction of the brush and slip ring. In addition to the wear of the brush, the momentary departure of the brush from the contact surface during rotation will cause electromagnetic noise generation.
When a slip ring is employed, noise will be overlaid on the signal to prevent accurate measurement. A weak signal cannot be transmitted/received. Furthermore, the spin finishing process is required when the brush and slip ring are attached. The ring must be attached accurately to prevent the departure of the brush.
In view of the foregoing, a main object of the present invention is to provide a bearing with a noncontant signal transfer mechanism that can transfer a signal in a noncontact manner without using a contact type brush and slip ring, or the like.
According to an aspect of the present invention, a bearing with a noncontact signal transfer mechanism transmitting a signal from a rotary shaft to a fixed shaft includes a power generation circuit generating power between the fixed shaft and the rotary shaft, and a signal transfer circuit transmitting a signal from the rotary shaft to the fixed shaft in a noncontact manner based on the power generated at the power generation circuit.
Since a signal can be transferred in a noncontact manner, the present invention is immune to the wear, noise generation, and attachment accuracy in the case where a brush and slip ring are employed.
The power generation circuit includes an annular permanent magnet provided at the fixed shaft, and a generator coil provided at the rotary shaft, generating power by rotating along the annular permanent magnet.
The power generation circuit includes a power feed coil wound around a yoke provided at the fixed shaft, and a power receiving coil wound around a yoke provided at the rotary shaft. A magnetic path is formed between the yoke of the fixed shaft and the yoke of the rotary shaft to output a current flow to the power receiving coil.
The signal transfer circuit includes a transmission coil wound around the yoke of the rotary shaft to transmit a signal, and a reception coil wound around the yoke of the fixed shaft. A magnetic path is formed between the yoke of the rotary shaft and the yoke of the fixed shaft to provide a signal corresponding to the signal flowing to the transmission coil to the reception coil.
The signal transfer circuit includes a transmission coil wound around the yoke of the rotary shaft to transmit a signal, and a magnetic detector element provided at the fixed shaft facing the transmission coil to detect change in the magnetic force of the transmission coil.
The signal transmission circuit also includes a light emitting element provided at the rotary shaft to emitt light according to a signal, and a light receiving element provided at the fixed shaft facing the light emitting element to receive light from the light emitting element.
The signal transfer circuit further includes a transmission circuit provided at the rotary shaft to transmit a signal through radio, and a reception circuit provided at the fixed shaft to receive a signal transmitted from the transmission circuit through radio.
The fixed shaft is an outer ring whereas the rotary shaft is an inner ring. A rolling element is provided between the outer ring and the inner ring.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.